I gave in a urine sample to the doctor this morning (first time I have ever done this) and I have just been told by the receptionist that they have sent it to a lab for further testing because something wasn't right with it.
What could this mean?

I am 34, male and have no symptoms of a urine infection - no burning or pain and the colour of my urine is fine. Any ideas? I really don't want to be worrying about this..

Thanks.